Moment frame links wall

ABSTRACT

A lateral bracing system having high initial stiffness and including yield links capable of effectively dissipating stresses generated within the lateral bracing system under lateral loads.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.13/214,000 filed Aug. 19, 2011 entitled MOMENT FRAME LINKS WALL, to beissued as U.S. Pat. No. 8,763,319, which is a continuation of U.S.patent application Ser. No. 10/847,851 filed on May 18, 2004 entitledMOMENT FRAME LINKS WALL, now U.S. Pat. No. 8,001,734, which applicationsare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to hysteretic damping for structures usedin light-framed constructions, and in particular to a lateral bracingsystem constructed to provide a high degree of energy dissipationthrough hysteretic damping along with high initial stiffness so thatenergy is dissipated at low force thresholds within a light-framedconstruction.

2. Description of the Related Art

Shear stresses due to natural phenomena such as seismic activity andhigh winds can have devastating effects on the structural integrity oflight-framed constructions. Lateral forces generated during such naturalphenomena may cause the top portion of a wall to move laterally withrespect to the bottom portion of the wall, which movement can result indamage or structural failure of the wall and, in some instances,collapse of the building.

In constructions such as residences and small buildings, lateral bracingsystems were developed to counteract the potentially devastating effectsof shear stress on the structural integrity of light-framedconstructions. Although various designs are known, typical lateralbracing systems include vertical studs spaced from each other andaffixed to horizontal top and bottom plates. The bottom plate istypically anchored to the floor diaphragm or foundation. The bracingsystem typically further includes sheathing affixed to the studs, upperplate and/or lower plate to increase structural performance underlateral forces. The sheathing used may be oriented strand board (OSB) orplywood, but fiberboard, particleboard and drywall (gypsum board) arealso used.

Alternatively or additionally, light-framed construction wall sectionsmay include lateral bracing systems in the form of prefabricatedshearwalls. Shearwalls within wall sections of light-framedconstructions provide lateral stability and allow the lateral forces inthe wall sections to be transmitted from the upper portions of the wallthrough the shearwalls to the floor diaphragm or foundation of thebuilding where they are dissipated without structural effect on the wallor building.

Many conventional lateral bracing systems perform well initially underlateral loads, but yield and fail upon the repetitive lateral loadswhich often occur during significant seismic activity and high winds.Upon appreciable yield or failure of the lateral bracing system, theentire system must be replaced.

It is known to provide conventional high strength walls that are capableof withstanding significant lateral loads that occur during seismic andother events. However, such walls place high demands on foundationanchorage and the foundation itself. Namely, the holdown bolts andfoundation must also be made strong enough to withstand the large forcestransmitted from the wall as they are dissipated through the holdownbolts and into the foundation. Therefore, while stronger wallsconventionally perform better under the seismic activity and otherloads, conventional design requirements attendant stronger walls cascadethroughout the entire structure, requiring stronger foundation anchorageand stronger foundations.

A further difficulty with conventional lateral bracing walls is that thecorners of such walls tend to bind against their support surfaces underlateral loads. FIG. 1 shows a conventional shearwall 20 mounted at itsbottom on a support surface 22 and at its top to a pair of top plates24. A lateral force F as shown will result in a downward force F1 atpoint A and an upward force F2 at point B. Under high lateral loads,these upward and downward loads can damage the wall 20 and/or thesupport structures above and below the wall.

SUMMARY OF THE INVENTION

It is, therefore, an advantage of the present invention to provide alateral bracing structure having high initial stiffness.

It is another advantage of the present invention to provide a lateralbracing system including controlled and predictable deflection and loadbearing characteristics of the wall member and controlled andpredictable yield of the yield links.

It is a still further advantage of the present invention to provide alateral bracing system where failure is limited to the yield links,which are easily replaced, thereby restoring the lateral bracing systemto its full load bearing capacity.

It is another advantage of the present invention to provide a lateralbracing system capable of fitting between conventionally located wallstuds, and which can be isolated from gravity loads.

These and other advantages are provided by the present invention, whichin embodiments relates to a lateral bracing system for use inconstructions such as light framed constructions. The lateral bracingincludes a structural moment frame supported between an underlyingsupport surface such as a building foundation and an upper supportsurface such as a top plate. The moment frame may be pivotally affixedto the underlying support surface by a pivot coupling, such as forexample a pin joint. The moment frame may similarly be affixed to theupper support surface by a second pivot coupling.

The lateral bracing system may further include a pair of yield linksaffixed between the frame and the underlying surface, one such yieldlink on each side of the moment frame. The yield link is provided toyield under a lateral load applied to the structural frame. Upon suchyielding, the pivot couplings allow the structural frame to pivot todissipate stress from within the structural frame. The yield links havea yield point below that of the moment frame, and will yield underlateral forces exerted on the lateral bracing system before the momentframe. Thus, damage to the moment frame is prevented by allowing themoment frame to pivot and dissipate the energy within the moment framewhich could otherwise damage the moment frame if it were allowed tobuild up beyond the yield point of the moment frame.

In an alternative embodiment of the present invention, a second pair ofyield links may be provided between the moment frame and the uppersupport surface to improve the rigidity of the structure while stillallowing the links to yield prior to damage to the structural momentframe. In embodiments including one or two pairs of yield links, in theevent the links are damaged upon yielding, the lateral bracing systemmay be restored to its virgin integrity and load bearing capabilitiessimply by removing and replacing the yield links. The structural frameneed not be replaced.

In another alternative embodiment of the present invention, the lateralbracing system may consist of a vertical column element coupled to ahorizontal beam element with a moment resisting joint. This momentresisting joint could consist of a central hinge, for example defined bya mounting element, with a pair of exterior yielding links, one oneither side of the central hinge. The bending strength of the column andbeam could be designed to exceed the moment capacity of the yieldinglinks, thus restricting damage in a lateral event to the links only.Furthermore, the beam could be configured to either run over the top ofthe column, or frame into the side of the column, without impacting theperformance of the connection via the yielding links.

Additionally, the moment resisting joint between the beam and columnalleviates the need for a similar connection at the column base, at, forexample, the foundation or lower floor. This means that forces thatwould otherwise be transmitted to the foundation or floor aredrastically reduced, and energy dissipation of a lateral event would becontained within the frame and not rely on a yielding connection to thesurrounding structure. Such a beam/column configuration may be used in avariety of applications, such as for example at the structural openingat garage fronts in light frame constructions, or around windows inlight frame constructions. In such an installation a column elementcould also be placed on either side of the beam element allowing for twoenergy dissipating joints in the assembly, each containing a pair ofyielding links.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to thefigures, in which:

FIG. 1 is a prior art front view of a conventional wall under a lateralload;

FIG. 2 is a perspective view of a lateral bracing system according to afirst embodiment of the present invention;

FIG. 3 is a front view of the lateral bracing system shown in FIG. 1,

FIG. 4 is a side view of the lateral bracing system shown in FIG. 2;

FIG. 5 is an enlarged partial perspective view of a bottom portion ofthe lateral bracing system according to the present invention;

FIG. 5A is an enlarged partial perspective view of a bottom portion ofthe lateral bracing system including yield links according to analternative embodiment of the present invention;

FIG. 5B is an enlarged partial perspective view of a bottom portion ofthe lateral bracing system according to an alternative embodiment of thepresent invention;

FIG. 6 is a perspective view of a lateral bracing system according to asecond embodiment of the present invention;

FIG. 7 is a front view of a lateral bracing system shown in FIG. 6,

FIG. 8 is a perspective view of the lateral bracing system according toa third embodiment of the present invention;

FIG. 9 is a front view of the lateral bracing system shown in FIG. 8,

FIG. 10 is a perspective view of a lateral bracing system according toan alternative embodiment of the present invention;

FIG. 11 is a front view of the lateral bracing system according to FIG.10;

FIG. 12 is a top view of the lateral bracing system according to FIG.10; and

FIGS. 13 through 15 are alternative embodiments of the lateral bracingsystem shown in FIGS. 10-12.

DETAILED DESCRIPTION

The present invention will now be described with reference to FIGS. 2through 15, which in embodiments of the invention relate to a lateralbracing system having high initial stiffness and including yield linkscapable of effectively dissipating shear stresses generated within thelateral bracing system under lateral loads. It is understood that thepresent invention may be embodied in many different forms and should notbe construed as being limited to the embodiments set forth herein.Rather these embodiments are provided so that this disclosure will bethorough and complete and will fully convey the invention to thoseskilled in the art. Indeed, the invention is intended to coveralternatives, modifications and equivalents of these embodiments, whichare included within the scope and spirit of the invention as defined bythe appended claims. Furthermore, in the following detailed descriptionof the present invention, numerous specific details are set forth inorder to provide a thorough understanding of the present invention.However, it will be clear to those of ordinary skill in the art that thepresent invention may be practiced without such specific details.

Referring now to FIGS. 2-4, there is shown a lateral bracing system 100including a moment frame 101 and yield links 110. Moment frame 101 is astructural frame including a substantially flat planar diaphragm 102bounded along each of its longitudinal edges by framing members 104.Diaphragm 102 and framing members 104 may each be formed of 7-gaugesheet steel (0.1875 inches). Other gauges, such as for example 10-gaugesheet steel, and other materials, such as for example sawn and/orengineered lumber may be used in alternative embodiments. Additionally,instead of the diaphragm and framing members being separate pieces, themoment frame 101 may instead by formed of a single rolled steel sectionhaving a C-shape or Z-shape in a horizontal cross-section. While framingmembers are shown only along the two vertical edges of diaphragm 102, itis understood that the framing members may additionally extend aroundthe top and/or bottom edges of the diaphragm 102 in alternativeembodiments.

Diaphragm 102 is mounted to a sill plate 106 by a pair of right anglebrackets 108, formed for example of ½ inch thick steel plate. Each ofthe right angle brackets 108 includes a first section mounted on sillplate 106 as by welding, bolting, gluing and/or other affixationmechanisms, and each bracket 108 includes a second portion extending upfrom the sill plate which is juxtaposed to each other in a spaced andparallel relation. The second portions of each of brackets 108 arespaced so as to receive a lower portion of diaphragm 102 therebetween.The diaphragm 102 may be fixed to the brackets 108 by a pivot couplingsuch as a pin joint formed by pin 109 (FIG. 5) fixed within a holeformed in each of the second portions of bracket 108 and the lowerportion of diaphragm 102. The pin joint allows pivoting of the momentframe under an applied lateral load. As explained hereinafter, the topof the moment frame may also be mounted to its support surface by apivot coupling allowing pivoting of the moment frame under lateralloads. As is also explained hereinafter, the top and/or bottom of themoment frame may be affixed with a fixed coupling instead of a pivotcoupling.

The pin joint fixedly mounts the diaphragm 102 to the brackets 108 andsill plate 106, but prevents stress between the diaphragm and thebrackets by allowing the diaphragm to pivot with respect to thebrackets. Thus, together with the yield links (explained hereinafter),the pin joint prevents damage to the moment frame 101, by allowing themoment frame to pivot, thereby preventing the build-up of large sheerstresses within the moment frame 101 that would otherwise occur if themoment frame were constrained from pivoting.

The bottom portion of diaphragm 102 has edges which slope upward from aneutral longitudinal axis of diaphragm 102 to framing members 104 asshown in FIGS. 2, 3, 5 and 5A. The slope prevents contact or binding ofportions of lateral bracing system 100 against the sill plate uponpivoting of the lateral bracing system under lateral loads. Such contactcould otherwise damage the moment frame, sill plate and/or theunderlying surface. The angle of the slope may vary in alternativeembodiments, from greater than zero degrees and higher from thehorizontal, and from about 2° to about 5° in further embodiments. It isalso contemplated that the bottom portion of the diaphragm 102 have noslope, but rather be horizontal to sill plate 106. Such an embodiment isshown for example in FIG. 5B. In such an embodiment, the bottom edge ofthe diaphragm may be flush against or slightly spaced from the sillplate.

Sill plate 106 is in turn affixed to an underlying surface by anchors130 as explained hereinafter. In embodiments of the invention, sillplate 106 may be formed of ½-inch thick steel. It is understood thatboth sill plate 106 and right angle brackets 108 may be formed ofthicknesses other than ½-inch, and/or materials other than steel, inalternative embodiments of the invention.

Yield links 110 are provided to dissipate shear stresses within lateralbracing system 100 generated by lateral loads, and to prevent the momentframe 101 from being damaged due to such sheer stresses. The lateralbracing system 100 exhibits high stiffness and rigidity for sheerstresses within the system below a threshold level. However, yield links110 have a yield capacity below bending strength of moment frame 101,and will yield under lateral forces exerted on the lateral bracingsystem before moment frame 101.

A lateral force on bracing system 100 will result in upward and downwardforces in the framing members 104 and along the longitudinal edges ofthe moment frame 101, as well as shear stresses within the moment framearound the neutral longitudinal axis of the moment frame. The upward anddownward forces are transmitted to and borne by the yield links 110.However, at lateral forces above a predetermined threshold, the yieldlinks will yield, allowing the moment frame to pivot around the pinjoint(s) and dissipating the shear stresses from within the momentframe. The pivoting allowed by the pin joint(s) and the yielding of theyield links thus prevents damage to the moment frame which may haveoccurred if the shear stresses within the moment frame were allowed toexceed the yield point of the moment frame. As explained hereinafter,the yield links 110 have a design allowing them to yield stably underboth tension yield and compression yield.

Embodiments of the present invention preferably include a pair of yieldlinks 110, one on either side of moment frame 101. For ease ofdescription, only one of the yield links 110 will be describedhereinafter. However, it is understood that the yield links areidentical to each other in embodiments of the present invention, and thefollowing description applies to both yield links. It is understood thatthe yield links may not be identical to each other in alternativeembodiments of the present invention. Moreover, it is contemplated thatlateral bracing system 100 includes only one yield link 110 on eitherside of moment frame 101 in alternative embodiments of the invention.

A yield link 110 is preferably formed of a yield member 114 mounted tothe lateral bracing system by an upper mount 112 and a lower mount 116.The yield member 114 may have ends which are threaded, so as to matewith threads within the upper and lower mounts 112, 116 to affix theyield member to the mounts. In such an embodiment, the threads atopposite ends of yield member 114 may be oppositely facing so that thedistance between mounts 112 and 116, and the forces within yield link110, may be adjusted by rotating yield member 114. It is understoodalternatively that yield member 114 may be affixed to upper and lowermounts 112, 116 as by welding, bolting, gluing and/or other affixationmechanisms.

Upper and lower mounts 112, 116 are preferably formed of steel. Yieldmember 114 may be formed of mild steel, such as for example ASTM A36steel. Other materials exhibiting stable yielding qualities and goodenergy absorption may alternatively be used for yield member 114,including other metals such as for example copper and bronze, andvarious polymers.

In embodiments of the present invention, a casing (not shown) may beprovided around yield member 114 so that yield member 114 and the casingtogether form an element with not only stable tension yielding behavior,but also stable compression yielding behavior because of the preventionof buckling by the casing. The casing in such an embodiment may beformed of various materials, such as concrete, a variety of polymers, orwood.

Whether formed of yield member 114 by itself, or as part of a bucklingrestrained element, the yield member 114 will yield stably, controllablyand predictably in tensile yields and/or compression yields uponapplication of lateral loads above a threshold level. The thresholdlevel at which the yield member will yield may also be controlled andpredictable based on the configuration of the yield link. The thicknessof the steel from which the yield member 114 is formed, as well as thelength of the yield member, may be optimized by computer modeling toprovide the desired performance and yield characteristics for yieldlinks 110.

If the moment capacity of the joints is known by virtue of the linkyield capacity and the physical geometry of the section, then the momentframe can be sized to exhibit elastic behavior even while the fullinelastic strength of the links are being taxed. In one embodiment,yield member 114 may be formed of 1 inch diameter steel, and the upperand lower mounts may be separated a distance of 6 inches. However, it isunderstood that the desired configuration of the yield links may vary inalternative embodiment.

Moreover, although yield link 110 is shown including a straight lengthof circular steel in the figures, it is understood that yield link 110may have various configurations in different embodiments of the presentinvention, with a provision that the yield link stably under lateralloads applied to lateral bracing system 100. For example, in oneembodiment, the straight yield member 114 may be replaced by a length ofsteel having a variety of configurations that will allow yield link 110to stably yield under lateral loads above predictable levels. The yieldmember 114 may include bends or a helix. It may also havecross-sectional shapes other than round in alternative embodiments, suchas for example that shown in FIG. 5A, discussed hereinafter.

Upper mount 112 may be affixed to frame member 104 as by welding,bolting, gluing and/or other affixation mechanisms. Lower mount 116 maybe affixed to sill plate 106 by mounting plates 118, which may be steelplates affixed to opposed sides of lower mount 116. Mounting plates 118may in turn be bolted to a U-shaped channel 120 by a pin joint includingpin 122 fixed within holes formed in opposed mounting plates 118 andopposed sidewalls of U-shaped channel 120. The pin joint allows pivotingof yield link 110 with respect to the U-shaped channel 120 and sillplate 106 to prevent generation of sheer stresses between yield link 110and U-shaped channel 120.

It is understood that lower mount 116 may be affixed to sill plate 106,either directly or indirectly, by other mechanisms in alternativeembodiments of the present invention. For example, in one suchalternative embodiment, the mounting plates 118 may be omitted, and ahole formed through the lower mount so as to allow the lower mount to beaffixed to the U-shaped channel 120 by pin 122. Moreover, it isunderstood that the pin joint may be omitted in an alternativeembodiment, so that the lower mount 116 is affixed to the sill plate 106without the ability to freely pivot with respect to the sill plate. Itis further understood that the upper mount 112 may be affixed to theframe member 104 by a pin joint between the upper mount and the framemember instead of or in addition to the pin joint mounting the lowermount 116 to the sill plate 106.

An alternative embodiment of a yield link in accordance with the presentinvention is shown in FIG. 5A. The yield link 160 according to thisembodiment may be formed from one or more flat plate elements 162 thatare affixed at one end to the frame member 104 by bolts, welding, gluingand/or other affixation means, and at the opposite end to the sill plate106 by bolts, welding, gluing and/or other affixation means. The flatplate element(s) may have a constant cross-sectional shape, or theelement(s) may have a central tapered midsection 164 similar to a milledsteel coupon sample. A buckling restraint stiffener 166 as shown mayfurther be provided. The buckling restraint stiffener 166 may be affixedto the frame member 104 as by bolting, welding, gluing and/or otheraffixation means. The buckling restraint stiffener shown has acorrugated cross-section, but it is understood that other cross-sectionsmay be provided to effectively restrain the flat plate element 162 frombuckling under compressive loads.

Sill plate 106 is mounted on an underlying support surface 126 by meansof anchors 130. In the embodiment shown, the underlying support surface126 comprises a concrete foundation, but it is understood thatunderlying support surface 126 may be any surface on which aconventional lateral bracing system may be located, for example, a floordiaphragm on the building foundation or a floor diaphragm on a top plateof a lower floor. Anchors 130 may be conventional anchors for mounting awall section to underlying support surface 126, and depending on thenature of support surface 126, anchors 130 may be for example strapanchors, mud sill anchors, retrofit bolts, foundation plate hold downs,straps, ties, nails, screws, framing anchors, plates or a combinationthereof.

The bracing system 100 may be attached to one or more top plates 128, asby bolts fitting through the top plates and into moment frame 101. It isunderstood that the bracing system 100 may be affixed to top plates 128by other mechanisms in alternative embodiments.

One such alternative embodiment for affixing bracing system 100 to topplates 128 is shown in FIGS. 6 and 7. The embodiment shown in FIGS. 6and 7 is substantially similar to the embodiments disclosed with respectto FIGS. 2-5, with the exception that moment frame 101 is affixed to topplates 128 via a pivot coupling such as a pin joint. In particular, themoment frame may be affixed to the top plates by a pair of right anglebrackets 140 similar in structure and operation to right angle brackets108. A pin 142 is received within aligned holes formed through brackets140 and a top portion of diaphragm 102 to affix the moment frame 101 totop plates 128. The pin joint allows pivoting of lateral bracing system100 with respect to top plates 128 without generating sheer stresses inthe diaphragm 102 or top plates 128. Thus, upon yielding of the yieldlinks as previously explained, damage to the moment frame is preventedby allowing the moment frame to pivot and dissipate the energy withinthe moment frame which could otherwise damage the moment frame if itwere allowed to build up beyond the yield point of the moment frame.

In embodiments, the top portion of diaphragm 102 has edges which slopedownward from a neutral longitudinal axis of diaphragm 102 to framingmembers 104 as shown in FIGS. 6 and 7. The slope prevents contact orbinding of portions of lateral bracing system 100 against top plates 128upon pivoting of the lateral bracing system under lateral loads.

As is further shown in FIGS. 6 and 7, the aligned holes formed inrespective brackets 140 for receiving pin 142 have an oblong shape. Thisshape significantly or entirely prevents vertical loads from top plates128 from being transmitted to lateral bracing system 100. Thus, onlylateral loads are transmitted. As explained hereinafter, the decouplingof vertical loads allows for easier control and predictability of theyield links performance.

As seen in FIGS. 6 and 7, the diaphragm 102 has longitudinal edges andframing members 104 which slope inward from bottom to top, for example,2 to 10 degrees from vertical. It is understood that the edge may bevertical (i.e. 0 degree slope) in alternative embodiments. It isunderstood that the embodiments described with respect to FIGS. 2-5above, and FIGS. 8-9 below may have similarly sloped edges.

A further alternative embodiment of the present invention is shown inFIGS. 8 and 9. The embodiment shown in FIGS. 8 and 9 is similar to theembodiments described above with respect to FIGS. 6 and 7, with theexception that a second pair of yield links 150 are provided. Yieldlinks 150 are mounted between moment frame 101 and top plates 128, andare structurally and operationally similar to yield links 110. Yieldlinks 110 and 150 together with framing members 104 define a structuralframe providing high initial stiffness and stable, controlled andpredictable yielding under lateral forces above a predeterminedthreshold level. The addition of the second pair of yield links improvesthe rigidity of the structure while still allowing the links to yieldprior to damage to the structural moment frame. It is understood thatyield links 110 may be omitted in alternative embodiments leaving onlyyield links 150 at the top of the moment frame.

The width of the lateral bracing system 100 may be such that it fits inbetween support studs formed in a wall. Thus, a plurality of lateralbracing systems according to the present invention may be providedwithin a wall to greatly enhance the ability of the wall to withstandlateral loads and sheer stresses. In one embodiment, the width of thelateral bracing system may be approximately 14 inches. However, thewidth may be greater than or less than 14 inches in alternativeembodiments. Moreover, the lateral bracing system 100 need not fitbetween support studs in alternative embodiments.

In accordance with the embodiments of the present invention describedabove with respect to FIGS. 2-9, lateral bracing system 100 hassufficient stiffness and rigidity to provide a high degree of resistanceto deflection under applied lateral loads. However, at lateral loadsabove a controllable and predictable level, the structure of the presentinvention provides for stable yielding of the yield links and deflectionof the moment frame. In this way, the applied lateral loads arehysteretically dampened from the system, and a high degree of energy isdissipated, thereby preventing damage to the moment frame 101.

Moreover, the energy dissipation provided by the yield links describedabove allows the lateral bracing system 100 to be designed to withstandlower sheer forces in comparison to conventional systems of similardimensions. This translates into lower design forces for the anchors andunderlying support surface as well. Thus, the reduction in design forceswithin lateral bracing system due to the yield links 110/150/160cascades throughout the entire design.

Furthermore, isolating the vertical loads with the pin joints at the topand/or bottom of the lateral bracing system allows for easy andpredictable control of various parameters of the lateral bracing system,including for example the initial stiffness of the lateral bracingsystem, the amount of deflection the top of the wall may undergo, theamount of force required before the yield links will yield, and peakanchor bolt demands. Moreover, the energy dissipation and stableyielding of the yield links allow the system 100 to withstand repeateddeflection under lateral loads without failure.

In the event the links are damaged upon yielding, the lateral bracingsystem may be restored to its virgin integrity and load bearingcapabilities simply by removing and replacing the yield links. Thestructural frame remains intact and need not be replaced.

In embodiments of the present invention discussed thus far, the lateralbracing system 100 has been comprised of a moment frame having yieldlinks affixed to either side. In further embodiments of the presentinvention, the lateral bracing system 100 may be formed of a verticalcolumn affixed to a horizontal beam by a moment resisting jointcomprised of a central mounting element and yield links on either sideof the mounting element. The moment resisting joint provides moment anddisplacement resistance between the beam and column, while allowingstable yield upon high lateral forces. Such embodiments are shown anddescribed hereinafter with reference to FIGS. 10 through 15.

Referring to FIGS. 10-12, there is shown a lateral bracing system 100including a vertical column 180 affixed to a horizontal beam 182 by amoment resisting joint 184 comprised of a central mounting element 188and yield links 160. Although referred to as a vertical column and ahorizontal beam, it is understood that the column and beam may beaffixed to each other by a moment resisting joint at angles other than90° in alternative embodiments. The moment resisting joint includesyield links 160, for example as shown and described above with referenceto FIG. 5A. In the embodiment shown, an end of the beam is mounted ontothe side of the column via an end plate 186. In such an embodiment, thepair of yield links 160 may be provided on top and bottom horizontalflanges of the beam 182 between the beam and the end plate. However, asexplained hereinafter, the beam may alternatively be on top of thecolumn so that an end of the column is mounted to a flange of the beamvia an end plate. In such embodiments, the yield links 160 would beprovided on respective vertical flanges between the column and the endplate.

As seen in FIGS. 10 and 11, the beam 182 may include a central diaphragmwith sloping edges as shown and as described above. A central point ofthe diaphragm may be affixed to end plate 186 via a mounting element188. The mounting element 188 may be no more than a welded seam, such asshown in FIGS. 10 and 11. However, it is understood that the centraldiaphragm of the beam may be affixed to the end plate by other types ofmounting elements, such as for example a pair of brackets having a pinjoint (FIGS. 5 and 5A) or a pair of brackets or plates not having a pinjoint, but instead simply affixing the diaphragm to the end plate as bybolts, welds, gluing and/or other affixation means (FIGS. 14 and 15).The end plate 186 is in turn affixed to a vertical flange of the column180 via bolts 192, welding, gluing and/or other affixation means. Theyield links shown in FIGS. 10-15 are those described above with respectto FIG. 5A. However, it is understood that any configuration of yieldlink described herein may be used in the embodiments described withreference to FIGS. 10-15.

In order to provide greater load-bearing capabilities at the jointbetween the column and beam, stiffeners 194 may be welded, bolted, gluedand/or otherwise affixed to the central diaphragm and flange of thecolumn 180. As seen in FIGS. 10-12, the stiffeners 194 are structuralpieces that extend perpendicularly from the opposed surfaces of thecentral diaphragm and flange on both the front and back surfaces of thediaphragm. Four such stiffeners are shown in FIGS. 10-12. The stiffenersmay extend partly across the column diaphragm as shown, or entirelyacross the diaphragm. FIG. 13 shows an alternative system to improve theload-bearing capabilities at the joint between the column and beam. Asshown therein, the portion 196 of the vertical flange in contact withthe end plate 186 may be made thicker. This may be done by removing thetop portion of the flange and replacing it with a thicker member, orotherwise fortifying the top portion of the flange. The portion 196 maybe used instead of or in addition to the stiffeners 194. It is furtherunderstood that the stiffeners 194 and/or thicker portion 196 may beomitted in embodiments of the present invention.

The moment resisting joint shown in FIGS. 10-13 provides high initialstiffness and resistance to relative movement between the column 180 andthe beam 182 under lateral loads, but provides stable yielding underlateral loads above a controllable level. In particular, bendingstrength of the column and beam could be designed to exceed the momentcapacity of the yield links. Thus, the yield links 160 yield underlateral loads before bending or deformation of the column or beam, andany damage is limited to the yield links which may be easily removed andreplaced. Furthermore, the beam could be configured to either run overthe top of the column, or frame into the side of the column, withoutimpacting the performance of the connection via the yielding links.

Additionally, the moment resisting joint between the beam and columnalleviates the need for a similar connection at the column base, at, forexample, the foundation or lower floor. This means that forces thatwould otherwise be transmitted to the foundation or floor aredrastically reduced, and energy dissipation of a lateral event would becontained within the frame and not rely on a yielding connection to thesurrounding structure. Such a beam/column configuration may be used in avariety of applications, such as for example at the structural openingat garage fronts in light frame constructions, or around windows inlight frame constructions. In such an installation a column elementcould also be placed on either side of the beam element allowing for twoenergy dissipating joints in the assembly, each containing of a pair ofyielding links.

In embodiments of the invention, it is understood that the portion ofthe central diaphragm which affixes to the sill plate (FIGS. 2-9) orendplate (FIGS. 10-15) need not have sloping edges. Such an embodimentis shown in FIGS. 14 and 15. In this embodiment, the central diaphragmof the beam may affix to the endplate as by a mounting element 188 inthe form of a plate which is bolted to the central diaphragm and weldedto the endplate. It is understood that the mounting element 188 may beaffixed to both the central diaphragm and endplate by bolting, welding,gluing and/or other mounting means in alternative embodiments. As bestseen in FIG. 15, a slight space may be left between the end of the beam182 and endplate 186 to allow rotation between the beam and column uponhigh lateral loads and yielding of the yield links without bindingbetween the column and beam. It is understood that the moment frame 101of FIGS. 2-9 may also be affixed at its top or bottom with aconfiguration as shown and described with respect to FIGS. 14 and 15.

Although the invention has been described in detail herein, it should beunderstood that the invention is not limited to the embodiments hereindisclosed. Various changes, substitutions and modifications may be madethereto by those skilled in the art without departing from the spirit orscope of the invention as described and defined by the appended claims.

What is claimed is:
 1. A lateral bracing system for use inconstructions, the lateral bracing system comprising: a structural framehaving a beam and a column; and a yield link affixed at a first end tothe beam and at a second end, opposite the first end, to the column, theyield link having a section between the first and second ends capable ofyielding in tension and compression to dissipate stress within the frameupon a lateral load applied to the structural frame.
 2. A lateralbracing system as recited in claim 1, further comprising a bucklingrestraint block affixed to the beam, the buckling restraint blocklimiting buckling of the yield link.
 3. A lateral bracing system asrecited in claim 2, wherein the buckling restraint block and yield linkbetween the beam and column allows omission of a lateral-torsionalbuckling restraint system on the beam.
 4. A construction including abeam and a column, the construction comprising: a yield link including afirst end affixed to the column, and a second end affixed to the beam,the yield link lying parallel to the beam and including a middle sectionbetween the first and second ends having a lower strength the yield linkand the first and second ends, the middle section capable of yielding intension and compression to dissipate stress within the construction upona lateral load applied to the beam and/or column. a buckling restraintblock affixed to the beam in a configuration sandwiching the yield linkbetween the buckling restraint block and the beam.
 5. A construction asrecited in claim 4, wherein the middle section has a smaller diameterthan the yield link at the first and second ends.
 6. A construction,comprising: a column; a beam; a shear tab affixed between the column andbeam; and a lateral bracing system affixed between the column and beam,including: a pair of yield links, each yield link including a first endaffixed to the column, and a second end affixed to the beam, a yieldlink of the pair of yield links having a middle section of smallerdiameter than at the first and second ends, the middle section capableof yielding in tension and compression to dissipate stress within theframe upon a lateral load applied to the beam and/or column. a pair ofbuckling restraint blocks, one each on a top and bottom flange of thebeam sandwiching the pair of yield links between the pair of bucklingrestraint blocks and the top and bottom flanges of the beam.
 7. A methodof assembling a frame having a beam, column and lateral bracing systemtherebetween, comprising the steps of: (a) affixing a yield link to thebeam, lying against the beam, the yield link including a middle sectionhaving a reduced strength relative to first and second ends on eitherside of the middle section; (b) affixing the yield link to the column;and (c) sandwiching the yield link between the beam and a bucklingrestraint block affixed over the middle section of the yield link.
 8. Amethod as recited in claim 7, said step (c) of affixing a bucklingrestraint block to the beam comprising the step of affixing the bucklingrestraint block by one of gluing or welding.
 9. A method as recited inclaim 7, said step (a) of affixing the yield link to the beam comprisingthe step of affixing the yield link to one of the beam prior to the beamand column arriving at a worksite.
 10. A method as recited in claim 7,the yield link affixed in said steps (a) and (b), and the bucklingrestraint block affixed in said step (c) together resisting lateraldeflection of the beam relative to the column, but yielding at themiddle section of the yield link upon loads above a threshold level.